Pressure release encoding system for communicating downhole information through a wellbore to a surface location

Abstract

A pressure release encoding system for communicating downhole information through a wellbore to a surface location include a downhole tool with a valve for providing a fluid restriction to fluid passing in the wellbore, a sensor positioned in the wellbore for sensing a downhole condition in the wellbore, a brake cooperative with the valve for moving the valve between at least two positions in timed relation to the downhole condition sensed by the sensor, and a detector positioned at the surface location for providing a measurement value at the surface location correlative to the time between the changes of the pressure of the fluid in the wellbore. The system associates position of the valve with pressure transduction. The sensor is an inclination sensor for sensing an angle of inclination of the wellbore.

1. A system for communicating downhole information through a wellbore to a surface location comprising:
 a drill string with a drilling sub at an end thereof; 
 a pumping means for pumping drilling mud into the wellbore, said drilling mud being fluid, said pumping means being positioned at the surface location and being in fluid connection with said drill string with said drilling sub; and 
 a downhole electronics module positioned in said drilling sub, said downhole electronic module comprising:
 a valve means for providing a flow restriction to fluid passing through said drilling sub, said valve means being suitable for controlling a flow of drilling mud in said drilling sub; 
 a sensor means positioned in the drilling sub for sensing a downhole condition in the wellbore; 
 a brake means cooperative with the valve means for fixing said valve means in at least two static positions, during a start of said flow of drilling mud through said drilling sub and during opening of said valve means; and 
 a detector means positioned at the surface location and cooperative with the fluid passing through said drilling sub for providing a measurement value at the surface location correlative to time between changes of pressure of the fluid in the drill string. 
 
 
     
     
       2. The system of  claim 1 , wherein said sensor means is comprised of an inclination sensor means, being housed within the drill sub and aligned with said wellbore and sensing an angle of inclination of said wellbore. 
     
     
       3. The system of  claim 1 , said valve means comprising:
 a housing positioned in said drilling sub; 
 a piston slidably movable in said housing; and 
 a piston stem connected to said piston and extending outwardly of said housing, said brake means acting on said piston stem so as to fix said piston in said housing in timed relation between the static positions. 
 
     
     
       4. The system of  claim 3 , said brake means comprising:
 an actuator piston bearing on said piston of said valve means so as to impede an axial advancement of said piston stem. 
 
     
     
       5. The system of  claim 4 , wherein said actuator piston is movable between a first stationary position and a second stationary position. 
     
     
       6. The system of  claim 4 , said brake means further comprising:
 a return spring being engaged to said actuator piston; 
 a differential pressure transducer, being positioned against said actuator piston; 
 a solenoid pilot valve means in communication with the pressure transducer; 
 a hydraulic fluid chamber, engaged to said solenoid valve means; and 
 a compensating piston, being actuated by said hydraulic fluid chamber. 
 
     
     
       7. The system of  claim 1 , said detector means comprising:
 a logic means for correlating a sensed time between controlled static pressure drops across the valve means to the downhole condition; and 
 a display means for providing a generally real-time humanly perceivable indication of the downhole condition. 
 
     
     
       8. The system of  claim 7 , said sensor means being an inclination sensor means for sensing an angle of inclination of said drilling sub in the wellbore, said inclination sensor means being aligned with said wellbore, said logic means for correlating said sensed time with said angle of inclination. 
     
     
       9. The system of  claim 1 , said brake means being a hydraulic brake and being comprised of a hydraulic chamber filled with oil, a sliding piston, a return spring and a control means for preventing displacement of oil when said sliding piston pushes against said oil. 
     
     
       10. The system of  claim 9 , wherein said control means is comprised of a solenoid-operated pilot valve and manifold.